Duplex loud talker



May 14, 1929. D, lA,

wH'rsoN 1,713,205

DUPLEX LOUD TALKER Filed April 11, 1923 I5 Sheets-,Sheet 1 May 14,1929 D. A. wHrrsoN y 1,713,205

` DUPLEX LOUD TALKER 4 mea April 11, 192s s sheets-sheet 2 May 14L1929- D.. A. WHITSON 1,713,205

ADUPLEX LOUD TALKER Filed April 1l, 1925 3 Sheets--Sheel 3 'Patented May 14, 1929.

UNITED STATES PATENT oFFlcE. I

i DELMAB A. WHITSON, F LOS ANGELES, CALIFORNIA, ASSIGNOR, BY MESNE .AISIGN- MENTS, TO THE MAGNAVOX COMPANY, OF OAKLAND, CALIFORNIA, A CORPORA- TION OF ARIZONA.

DUPLEX LOUD TALKER.

My invention relates tothe art of telephony and more particularly to loud talkers of the type employed in the receivmg of lradlo sound transference. Although such devices have their particular utility in the art of radlo telephony in which they areemployed with receiving sets for the purpose of rendering the sounds transmitted by 'the .radio audible to persons situated at some distance from the receiving device, loud talkers of the type herein described may be employed with any electrical sound transmitting device.

It is an object of the invention to provide a loud talker which is extremely simple in construction and therefore may be distributed at a 'low cost.y

It is a further object of the invention to provide a device of thischaracter which will deliver sound ampliications which may be heard throughout a large sized room without the use of auxiliary batteries to `provide booster' current.

It is a further object of the invention to provide a simplified form of magnet and means therewith whereby an armature may be caused to move integrally instead of pivotally as now customary in loud talkers, thereby substantially doubling the amplitude of vibrations delivered and thereby eliminating 3o the need for an auxiliary battery in order to give the desired strength'of sound delivered by the loud talker. v

It is a further object of theinvention to provide in this simplified form-of device an arrangement whereby the armature is suspen ded in opposing magnetic fluxes which are in constant balanced relationship, when not infiuenced by the exciting magnetism induced i'n the armature by the exciting coil, thus 40 making it impossible for residua-1 magnetism to build up within the armature and affect thef operation thereof.

It is a further object of the invention to provide a simplified form of construction in which the operating elements of the device are mounted upon the underside of a cover plate and are removable therewith from the shell, which construction facilitates the assembling of the device and makes the operating elementseasily accessible.

lIt'is a further 'object of the invention to provide an improved form of diaphragm which'will impart-to the amplifier horn and 1923. Serial No. 631,317.

the air column therein stronger vibrations than are rendered by the common form of diaphragm.

The specific advantages ofthe invention and further objects thereof will be made evident hereinafter.

Referring to the drawing which is for illustrative purposes only Fig. 1 is a partially sectioned view of a loud talker embodying the features of my invention.

Fig. 2 is a view looking at the underside 65 of the cover plateand sectioned as indicated by the line 2-2 of Fig. 1. i

Fig. 3 is a section taken upon a plane represented by the line 3 3 of Fig. 2.

. Fig. 4 is a perspective view showing the im- 70 proved form of fixture which I employ.

F 1g. "5 is an enlarged vfragmentary elevation illustrating the manner in which the exc1t1ng coils are mounted in the magnetic field and the manner in which the armature is supported.

' Fig. 6 is a diagrammatic view illustrating the magnetic action which takes place in the magnetic field in which the armature is Suspended.

Fig. 7 is a view similar to Fig. 2 showing f' another form of construction which permits the exciting `coil to be made in continuous length.

Fig. 8 is a section taken on a plane reprel sented by theline 8-8 of Fig. 7.

Fig. 9 is a sectional View similar to Fig. 3 showing an improved manner of supporting the armature in such a way that a direct thrust is delivered by theV armature to the diaphragm.

Fig. 10 shows an'improved form of magnet construction which facilitate the construction shown in Fig. 9 and makes it ossible to l extend the two coil members constltuting the energizing coil substantially .the full llength of the armature. A

Fi 11 is a view showing the manner inr whic the coil members shown in Fig. 10 are placed between the arms of the magnet fixture.

Fig. 12 is a section taken on a plane represented by the line 12--12 in Fig. 9, showing the form of torsion plate employed.

Fig. 13 is a partially sectioned detail'showling adiaphragm embodying my vimproved construction.

Fig. 14 lshows a simple form of diaphragm embodying the characteristics of the diaphragm/ shown in Fig. 13.

As shown in Fig. 1 of the drawing my deviceeinploys a shell 12 having a weighted base 13 and a removable cover member 14. This cover member as shown in F ig. 3 is provided with an extension 15 in which the horn 16y may be secured. The underside of the cover plate 14 is recessed as indicated at 17 and a diaphragm 18 is secured thereacross by a clamping ring 19 which compresses an annular gasket 20 against the circular edge oi the diaphragm 18. The clamping ring 19 is se- Y members 24 are provided with outwardly extending ears 25^drilled as indicated at 2G for the passage of the screws 27 and upwardly oifset from the central portion 28 through the formation of a vertical wall 29. Do'w'nwardly extended from the central portion 28 is a tongue 30 having a threaded opening 31 therein by which the xture is secured to the end of the magnet 23 by screws 32 which extend through holes provided in the ends of the magnet and thread into the openings 31. At one side of the central portion 28 an arm 33 extends inwardly while at the opposite side an arm 34 which is downwardly offset as shown in Fig. 4 also extends inwardly in a horizontal position but at a plane below the plane of the arm 33.

It will be seen that when a pair of the fixtures 24-are mounted upon the ends of the magnet 23 as shown in Fig. 1 and Fig. 5 the arms 33 of the two fixtures will lie in the same plane while the arms 34 thereof will lie in a lower plane. The lengths of the arms are such that they .overlap in the manner shown in Fig. 1 and are spaced apart to such an extent that an armature 37 may extend between the ends thereof. By means of a spacer 38 a pair of cooperative exciting coils 39 are held spaced apart between the ends 33 and 34 of the fixtures 24'. This i'ixture 38 is bent from sheet brass and' has a portion 40 thereof whichslightly greater than semi-annular extension as shown in 5, thus providing an open space 41 between the coils into which the rod 42 extends between the armature 37 and the diaphragm 18 and also through which extends the armature supporting member 44. This armature supporting member 44 provides two perpendicularlv extending legs one of which is secured to the center of the armature 37 and the other of which is secured to one of the fixtures 24 by means of a small screw 45. As hereinbefore mentioned, the. fixture 2 4 is designed to control the iiow oi' magnetic iux between the ends of the magnet 23. W'ith reference to Figs. 1 and 6, this feature may be explained. Let us consider that the left-hand pole 50 of the magnet 24 is north, and that the right hand pole 51 thereof is south or negative. The flow of magnetic flux between the poles 50 and 51 is from north to south and therefore the iux will flow outwardly through the arm 33 nearest the observer andwill thence drop downwardly to the arm 34 cooperating therewith through which it is carri/ed to the pole 51. The left ends of the arms 33 and 34 are iepresented at the left hand side of Fig. 6, or in other words. at 52. It will be evident that the right ends ofthe arms 34 represented at the right hand side 53 of Fig. 6 are a portion of the fixture 24 from which the left hand arm 33 extends. Therefore this arm will also constitute a north pole while the arm 33 situated thereabove and extending from the xture 24 from which the south pole on the left hand side also extends, will in turn be a south pole. Therefore, from a magnet 23 having a north and south pole, we obtain a divided flow of magnetic fiux, one .of these iiows of magnetic flux being in a downward direction at the left handV side 52 and the other flow of flux being upwardly at the right hand side 53. In this manner'two oppositely flowing fluxes are derived from the same magnet which insures that the strength thereof will remain equal at all times which is highly essential to the efficient operation of the device. y The armature 37 has the end 55 thereof in the p'ath of a downwardly flowing flux as indicated by the arrows 56 while the'opposite end 57 is disposed in the path of an upwardly flowing flux indicated at 58. The armature 37 h/owever provides a path through which magnetic fiux may iow between the poles 33 and between the poles 341 this'ow of fiux being in opposite directions as indicated by the arrows 59 and 60. They 'through the coils 39 is such that the end 55 becomes a north pole andthe end 57 thereof becomes a south pole. It will be perceived that both ends ofthe armature will be drawn downwardly while with a reversal/of the polaritv of the armature 37, it will move upwardly toward the members In this manner a direct thrust is imparted to the connecting member 42 and by this arrangement, the greatest force with the least expenditure of electrical lenergy isobtained.- Certain.

- the arrows 59 and 6() through the armature vmetal as'shown in Fig. 12.

37 provides a neutralization of the magnetic condition within the armatureand thereby prevents the building up of residual magnetism therein. This feature sustains the maximum of activity of the armature and prevents it becoming sluggish after being in use for a period of time, owing to residual mag- .netism.

In Figs. 7 and 8 I show a form of my invention in which an exciting coil is employed which extends over a greater length of the armature 37 than it is possible with'the divided construction shown in the previous figures. The coil 65 is wedged between the arms 33 and 34 and the armature 37 extends therethrough and is equipped with a yoke 66 which is securedto the ends of the magnet by means of small screws 67. A flexible arm 68 extends from one-'side ofthe yoke 67 and is secured to a. post 69 as indicated in Fig. 8. It will be noticed that the arm 68 prevents lateral movement of the armature 37 and causes it to swing in a slight are when vibrating. The action of the armature transferred to the diaphragm 18 through the yoke 66 is substantially direct, however.

The form of the invention shown in Fig. 9 provides `very efficient results. In this form of construction, the tongues 300f the fixtures 24 are extended downwardly, as shown, and

i the connecting member 7() by which the armature 37 is linked to the diaphragm 18 is pro-` vided in the form of a rod which continues through the armature 37 and is secured at 71 to a torsion member 72 'in the for-'m of a plate which is mounted upon the lower end of the downwardly extended tongues 30 by means of a small screw 73 or other attaching means.

The torsion member 72 is formed fromy sheet The particular advantages and benefits derived from the use of the torsion member for supporting the connecting member are evident in the enhanced tone values produced, the sensitiveness of the torsion member in response to vibrations of small amplitude allowing a free movement of the diaphragm for softV tones, and the rapid increase in resista-nce of the member under torsion as the 'amplitude'of the vibrations increases effectually preventing interference due to the armature 37 striking the arms 33 and34.

` It will be seen that by this construction a Qvery direct action between the armature 37 Y l andthe diaphragm .and a rigid structure are ned which eliminates aberration inthe use of the device. There are no pivots em .ployed in any of the construction shown. I

have found that the use of pivots is undesirable owing to the fact that side movement and .aberration in the vibration .results which causes a series reduction of the tone quality.

lIt is very desirable'that the exciting coil extend over the greatest length of the armature post. In Fig. 10 I show a pair of spools 8() and '81 upon which the exciting coils are wound. The spool is provided with thin flanges .as shownnvhile the inner flange 82 of the spool 81 is of increased thickness and has a vertical channel 83 cut therein. It Will be recognized thatwhen the spools are placed together and wedged between the arms 33 and 34 of the fixtures`24 as shown in Fig. 11 that the flange 82 of the spool 81 will bear against the flange ofthe spool 80 and that the channel 83 thereupon provides a passage through which the connecting rod 70 may extend. This construction entirely eliminates the spacing member 40 and provides 'a more efficient and durable form of construction than can be accomplished by the use of such a fixture shown at 40.

The improved form of diaphragm which I employ is shown at Fig. 13. This diaphragm 18 is constructed from a central plate ofvbake: lite impregnated silk 84 having two plates 86 of the same material and of smaller diameter placed centrally upon either side thereof.

This construction provides a quite rigid central portion'87 .and aflexible radially extended web 88. Substantially all of the iiexure in this diaphragm occurs within the flexible .extending web 88 and the central portion 87 moves substantially as a flat piece. In the or-` dinary type of diaphragm, the flexure at the fcenter of the diaphragm is greatest and drops oli regularly as the extremity thereof is approached.. Therefore, it will be recognized that the amplitude Aof the vibrations imparted to the air column of a horn is greatest at the same amplitude as those vibrations imparted vin the center. Therefore, I am able to obtain a larger tone volume from the same vibrated source than is possible by the use of the 'standard form of diaphragm. It is my belief also that this form of construction gives a higher and greater tone quality.

f The form of my diaphragm invention shown in Fig. 14 is somewhat simplified in construction, but is very satisfactory in operation and has greater durability than the type shown in Fig. 13; Three plates 90, 91v

bility adjacent to the edge in which substantially all of the vibrator-y movement is taken. The center plate 91 is imperforate, thus providing a continuous diaphragm wall to prevent interference due to passage of air.

I claim as my invention:

1. In a loud talker, thecombination of: means for producing a pairpf adjaeentlydisposed magnetic fields of relatively opposite polarities, said magnetic fields being excited by a single magnet; 4an armature having one pole thereof iii one of said magnetic fields and another pole thereof in the other of said magnetic fields; and means for producing a magnetic polarity of yarying intensity in said armature.'

2. In a loud talker, the combination of: means for producing a pair of adj acently disposed magnetic fields of relatively opposite polaritie's,/said magnetic fields being excited by a single magnet; an armature having 'one pole thereof in oneof said magnetic fields and the other pole thereof in the other of said magnetic fields; and an exciting coil t for producing a magnetic field of varying intensity in said armature. Y y y 3. In a loud talker, the combination of :i means for producing a pair of Iadjacently disposed magnetic fields of relatively `oppo` site polarities, said magnetic fields being excited by a single magnet; an armature having one pole thereof in one of said magnetic fields and the other pole thereof in theffother of said magnetic fields; an excitingfeoil for producing a magnetic field of varying intensity in said armati-1re; a sound reproducing diaphragm; and a lmemberlinking between .-said armature and said diaphragm ferim- ,parting the vibrations 0f said Aarmature to" said diaphragm.

"4. In a loud talker the combination of: a permanent magnet having the ends thereof adjacently disposed; pole fingers extending inwardly from the positive poleof said magnet; co-operating pole fingers extending inwardly from the negative pole of said mag-l net, one ofsaid ycooperating pole fingers being extended above the opposing pole finger extending inwardly from said positive pole offsaid magnet, and the other of said cooperating pole fingers extending below-the opposlin g p ole finger extending inwardly from said positive pole; an armature having one Y pole thereof disposed between one pair of positive'and negative pole fingers, and having i the other pole thereof' disposed 'between the other pair of positive and negative' pole fingers; and means for imposing a magnetic fieldl of varying intensity in said armature.

5. In a loud talker, the combination of: a permanent magnet having the ends' thereof adj aeent-ly disposed ;pole fingers extending inwardly from the positive pole of said magnet;

eco eratine 'Dole fingers extending inwardl y L! h= D from the negat-ive pole of said magnet, one of said cooperating pole fingcrsbeing extended above'tlie'opposing pole finger extending inwardly from said positive pole of'saidl inagnet, and the other of said cooperating pole fingers extending below the opposing pole finger extending inwardly from said positive pole; an arinatuie having one pole thereof disposed between one pair of positive and negative pole fingers, and having the other pole thereof disposed between the other pair of positive and negative pole fingers; and anr excitingcoil for imposing a magnetic field of varying intensity in said armature.

6. In a loud talker, t-he combination of: a

`permanent magnet having the ends thereof adjacently disposed; pole fingers extending inwardly from the positive pole-of said inagnet; cooperating pole'fingers, extending inwardly from the negativepoleofsaid magnet,

:fingers extending below the opposing pole finger extending inwardly from said positive pole; an armature having one pole thereofdisv I p osed between one pair of positive and negative pole fingers, and having the other pole thereof disposedv between the other pair of positive and negative pole fingers; an exciting coil for imposing' a magnetic fieldjof"` varying intensity in said armature; asound reproducing diaphragm; and a member link- .ingbetween said armature and said diaphragin Afor imparting the vibrations of said y armature to said diaphragm.

7..In a loud talker, the combination aof:

a permanent magnet having the ends thereof adjacently disposed;- pole 4fingers extending inwardly from the positive pole of said magnet; cooperating pole fingers extending inwardly from the negative pole of said magnet, one of said cooperating pole4 fingers being extended above the oppesing pole fifngerex-` tending inwardly from said positive pole`l of said magnet, and the other of said cooperating polefingers extending below the opposing pole finger extending inwardly from said positive pole; an armature having one -pole thereof disposed between one pair of positive and n egative` pole fingers, and having the other pole thereof disposed between the other pair of positive and negative pole fingers; an

exciting coil for imposing amagnetic field of varyingeintensity in -said armature; a sound l reproducingdiaphragm; a Amember linkingV between said armature and said dlapnragm' for imparting the vibrations of said armature to said diaphragm; and a torsion plate for stabilizing and controlling the movement of s aidl linking member.

8. In-a loud talker, the combination of; a permanent magnet having the ends thereof adjacently disposed; pole fingers extending inwardly from the positive pole of said magv net; cooperating pole fingers extending inwardly from the negative pole of said magnet, one of said cooperating pole fingers being extended above the opposing pole linger extending inwardly7 from said ositive pole-of said magnet, and the other of said cooperating pole fingers extending below the opposing pole finger extending inwardly from said positive pole; an armature having one pole thereof disposed between one pair of positive and negative pole fingers, and having the other pole thereof disposed between the other pair of positive and negative pole lingers; an exciting coil for imposing a magnetic field of varying intensityin said armature; a sound reproducing diaphragm; a member linking between said armature and said diaphragm for imparting the vibrations ofsaid armature to said diaphragm; a diaphragm; and a link joined at one end to said diaphragm and` joined to the center of said armature; and a torsion member for stabilizing and controlling the movement of said linking member.

9. YIn a loud talker, the combination of: a permanent magnet having the ends thereof adjacently disposed; pole fingers extending inwardly from the positive pole of said magnet; cooperating pole fingers extending inwardl from` the negative pole of said magnet, one o said cooperating pole fingers being ex- I tended abovethe opposing pole linger extending inwardly .from said positive pole of said magnet, and the other of said cooperating pole fingers extending below the opposing pole finger extending inwardly from said positive pole; an armature having one pole thereof disposed between one pair of positive and negative pole fingers, and having the other pole thereof disposed between the other pair of `positive and negative pole fingers; an exciting coil for imposing a magnetic field of varying intensity in said armature; a sound reproducing diaphragm; a member linking between said armature and said diaphragm for impartin the vibrations of said armature to said `diaphragm; a diaphragm; a link joined at one end to said diaphragm and joined to the center ofv .said armature, said link being substantially rectilinear and extending to a point below said armature; and

-a torsion plate secured at the lower end of said link, forl controlling the movement of said link g.l I I.

permanentmagnet having substaniwardlyjfrom-the poles thereof," said pole 4;,p, ,iece 's1h'giving each two limbs, said limbs being offset and spaced apart from each other alternately, so that two limbs, each one belonging to a different pole piece and having dissimilar poles, shall lie ad]acent each other upon each side of a center plane, an armature having its plane lying substantially in the center plane, a coil for energizing said armature,- and means, connected to said armature, for producing sound waves in harmony with said impulses.

11. A telephone receiver comprising a diaphragm, an energizing coil, an armature therefor having a rigid connection with the diaphragm, a permanent magnet, and divided pole pieces at each end of said permanent magnet, the members of each pole piece being disposed on opposite ends and opposite sides of the armature.

12. A telephone receiver comprising a diaphragm, an energizing coil, an armature therefor having a rigid connection with the diaphragm, a permanent magnet and U- shaped pole pieces at the ends of said permanent magnet having their arms crossed so that `arms of opposite polarity are disposed at opposite ends of the armature and on the same side thereof.

13. A telephone receiver of the vibrating armature type embodying U-shaped pole g pieces whose arms co-act to form an air gap at opposite ends of the armature, each pole piece having one arm positioned on one side of the armature and the other arm positioned on the opposite side thereof, and a permanent magnet to which said U-shaped pole pieces are connected at opposite ends.

14. A telephone receiver of the vibrating armature type comprising a diaphragm, an armature, a rigid connection between the armature and diaphragm, energizing coils surrounding the armature and arranged on opposide sides ofsaid rigid connection, apermanent magnet having U-shaped pole pieces whose arms co-act to form air gaps at opposite ends of the armature, each pole piece having one arm positioned on one side of the armature iand the other arm positioned on the opposite side thereof.

15. In a receiver of the balanced armature type, a polarizing magnet, each pole of said magnet being provided with U-shaped pole pieces, an armature for said receiver, a solenoidal winding over said armature but free therefrom, a diaphragm included in sald receiver, and a rigid connection between said armature and the diaphragm, said armature and pole pieces being so arranged that one end of the armature is over and the other end of the same is under the respective legs of each pole piece.

16. In a telephone receiver of the balanced armature type, includinga soun-d box, a diaphragm, a solenoidal w1ndinga soft iron armature extending through said winding but free therefrom, and a polarizing magnet,

said magnet having branched pole pieces, one of which branches is under one end of the armature and the other branch of which is over the opposite end of said armature.

17. A telephone receiver comprising a frame, a diaphragm thereon, energizing coils, an armature extending through said coils, a mechanical connection between the armature and the diaphragm intermediate the ends of said armature, a permanent magnet having divided pole pieces at its ends, the members of each pole piece being disposed on opposite ends and opposite sides of the armature, and means for anchoring the armature at one or both ends beyond the pole pieces.

18. An electromagnetic system comprising an armature, a magnet having a plurality of pole pieces concentrated at opposite sides of said armature, two of said pole pieces on one side being of opposite polarity, two of said pole pieces on the other side being of opposite polarity, each of said pole ieces being directly opposite a pole piece of t e opposite polarity, and an alternating current windin cooperating with said armature.

19. An electromagnetic system comprising an armature, a magnet having a plurality of pole pieces concentrated at opposite sides of said armature, two of said pole pieces on one side being of opposite polarity, two ofsaid pole pieces on the'other side being of opposite polarity, each of said pole pieces being directly opposite a pole piece of the opposite polarity, and an alternating current winding surrounding said armature and located between pole pieces of opposite polarity on each side of said armature.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 6th day of April, 1923.

DELMAR A. WHITSON. 

